Re: [PATCH v15 28/37] KVM: arm64: CCA: Support RSI_HOST_CALL

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 15/07/2026 15:28, Steven Price wrote:
> From: Joey Gouly <joey.gouly@arm.com>
> 
> Realm VMs can talk to the hypervisor using the RSI_HOST_CALL SMC. The
> RMM forwards this to the host and KVM handles them as regular
> hypercalls.
> 
> Signed-off-by: Joey Gouly <joey.gouly@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> ---

minor nit: Populating the results back to the Realm is added in the 
Patch 14: KVM: arm64: CCA: Handle realm enter/exit

May be a good idea to move to this one here ?

Either ways:

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

> Changes since v7:
>   * Avoid turning a negative return from kvm_smccc_call_handler() into a
>     error response to the guest. Instead propagate the error back to user
>     space.
> Changes since v4:
>   * Setting GPRS is now done by kvm_rec_enter() rather than
>     rec_exit_host_call() (see previous patch - arm64: RME: Handle realm
>     enter/exit). This fixes a bug where the registers set by user space
>     were being ignored.
> ---
>   arch/arm64/kvm/rmi-exit.c | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/arch/arm64/kvm/rmi-exit.c b/arch/arm64/kvm/rmi-exit.c
> index c668cbfa971a..78d9189fd5ca 100644
> --- a/arch/arm64/kvm/rmi-exit.c
> +++ b/arch/arm64/kvm/rmi-exit.c
> @@ -113,6 +113,19 @@ static int rec_exit_ripas_change(struct kvm_vcpu *vcpu)
>   	return -EFAULT;
>   }
>   
> +static int rec_exit_host_call(struct kvm_vcpu *vcpu)
> +{
> +	int i;
> +	struct realm_rec *rec = &vcpu->arch.rec;
> +
> +	vcpu->stat.hvc_exit_stat++;
> +
> +	for (i = 0; i < REC_RUN_GPRS; i++)
> +		vcpu_set_reg(vcpu, i, rec->run->exit.gprs[i]);
> +
> +	return kvm_smccc_call_handler(vcpu);
> +}
> +
>   static void update_arch_timer_irq_lines(struct kvm_vcpu *vcpu)
>   {
>   	struct realm_rec *rec = &vcpu->arch.rec;
> @@ -188,6 +201,8 @@ int handle_rec_exit(struct kvm_vcpu *vcpu, int rec_run_ret)
>   		return rec_exit_psci(vcpu);
>   	case RMI_EXIT_RIPAS_CHANGE:
>   		return rec_exit_ripas_change(vcpu);
> +	case RMI_EXIT_HOST_CALL:
> +		return rec_exit_host_call(vcpu);
>   	}
>   
>   	kvm_pr_unimpl("Unsupported exit reason: %u\n",